Considering that only 8 people survived, I'd imagine they would've thought they were the chosen ones and God smited the rest.

The eight survivors in this case survived because they understood what was happening and fled to high ground though.

If you knew stories about the lake, wouldn't you try to get away from it? And by the pictures away <==> up in most cases. Also, I feel like at least my flight instinct prefers higher ground.

Not saying the 8 survivors didn't know what's up, but stuff like this is definitely how religious stories get formed in general.

Natural instinct is to run away.

It's like how the smart thing to do is run to the side of a tree that's starting to fall over (perpendicular to it's projected fall).

A good way of describing it to the locals might be that 'bad gasses come from the lake and cling to the ground, like a leaden miasma from hell'.

You don't want to be very close to a tree that is falling over because of the way the roots tear up the ground. Or, if the tree has been cut down and its direction of fall is not clear of obstructions, the cut end of the trunk could fly around in unexpected ways. Best to be well clear on the far side of the direction of fall.

Interesting, how they were able to realize what's going on.

Wiki tells that one loses conscience after couple of inhales of CO2.

I assume that those folks went on high ground just after they've heard sound.

The article says how: "evil spirits."

I don't think you'd necessarily have to know a lot about chemistry, just some observation of volcanism. The ancient Grecian knew that ground vents & volcanoes produced noxious fumes (e.g. hydrogen sulfide), and that volcanoes can explode and kill people in fairly obvious ways.

Not to say you could have figured out the carbon dioxide part, but you could have developed an understanding deeper than "god" or "spirits".

It's easy to say so with the benefit of hindsight and centuries of accumulated scientific knowledge, but I'd say it's pretty understandable to pin such an odd and eerie event on an "evil spirit" or something similar.

I'm sure humans in several hundred years will be able to take a similarly hindsighted stance on the things that we don't have explanations for today.

"I mean, you don't have to know about quantum mechanics, but honestly thinking that there's some magic invisible energy causing the universe to expand? I mean seriously, I think I probably could have come up with some kind of explanation better than 'Dark Energy.'"

There will still be only 1% of people aware of the phenomenon at all.

The article says they're not sure if it was volcanic activity that triggered the release, or something else.

The scholars writing for posterity may have known that. Everyone else might not.